A Capitol Hill source close to meetings between lawmakers and administration officials said the officials “were clearly feeling all the pressure.”

“Since the bill was first introduced in February, my staff has worked around the clock to find five Republicans votes necessary to reach that number,” Feinstein said in a rare public appeal. “We are very close to 60, but we’re not there yet.”

Written by conservatives from the Central Valley, the House bill would mandate more water shipments from the delta to San Joaquin Valley farms and override the Endangered Species Act.

Feinstein’s bill would increase “flexibility” for agencies to manage the drought, a term that has come to mean easing environmental rules to increase water deliveries. She dropped spending for some projects from her bill to allay GOP budget concerns.

Environmentalists have grown increasingly skeptical of Feinstein’s negotiations with House Republicans.

“Frankly most of what’s left (in Feinstein’s bill) is provisions regarding the minutiae of Endangered Species Act implementation,” said one environmental lawyer who did not want his name used. “To be blunt, we’re trying to figure out what’s intended by those and we don’t have a good answer.”

The maneuvering has also hardened environmentalist opposition to Gov. Jerry Brown’s twin-tunnel project to bypass the delta and take water south. Environmentalists said relaxation of wildlife protections during the drought belies promises by tunnel backers that the project will lead to habitat restoration in the delta.

The cnvironmental lawyer added, “If the whole idea of the governor’s twin tunnels is to build a large facility and then to trust that it be operated in a way consistent with best available science, it’s tough to trust that will happen if Congress simultaneously is dictating operation of the project.”

A new report by the Center for Responsive Politics and Southern California Public Radio shows that the 600,000-acre Westlands Water District, representing farmers in Fresno and Kings Counties, has spent a record $600,000 on lobbying this year.